The U.S. Pat. No. 8,845,469 B2 filled May 31, 2011, describes a double planetary gear mechanism for hybrid vehicles, while the U.S. Pat. No. 8,840,499 B2 filled Feb. 13, 2012 is about how to store and recover kinetic energy from the generator rotor. The present invention combines the two devices and makes them work on a pulsatile way that is new.
Compare to the French patent application FR 14/01 126 filled on May 19, 2014 about the same topic, the present invention is more complete. Particularly in a new option, the invention is applied to the thermodynamic cycles in each engine cylinder instead to the whole engine.
The hybridization of a vehicle consists to associate a thermal propulsion chain to an auxiliary propulsion chain which can be electric, hydro pneumatic or mechanic. The auxiliary propulsion chain allows shifting the operating point of the thermal propulsion chain to make it work under better conditions at higher efficiency. Generally, best efficiency is obtained by lowering engine speed and by increasing its torque for the same output power. Unfortunately, at low vehicle speed, the engine speed can't be lowered below its stability limit, around 800 rpm. That limits benefit of vehicle hybridization. The usual solution at low speed is to stop the thermal propulsion chain and to continue with the auxiliary propulsion chain only. This last is less powerful and well adapted to low power. Of course, this option is limited by the stored energy to be consumed in the auxiliary propulsion chain, and the engine has to be restarted soon. This technique is commonly known as “stop and start.” If the storage capacity is small, frequency of the stops and starts has to be high, looking as pulsations.
Stop and start technique is used whatsoever power-train architecture is: parallel, series, series-parallel, etc. . . . and whatsoever auxiliary energy is: electric, mechanic, hydra-pneumatic, etc. . . . . But, it has some important disadvantages. Numerous stops and starts disturb smooth driving and punctually increase fuel over-consumptions and CO2 emissions. Benefit balance is not always positive. It depends of the driving style and the road profile. In addition, heavy and costly energy storages are required.
In the patent application FR 12 58707 dated Sep. 17, 2012, WO 2014/041275 A1 issued on Mar. 20, 2014, the low capacity of hydra-pneumatic storage is compensated by frequent engine stops and starts. Higher the frequency is, less positive the benefit balance is.
Many power-train architectures and storage types exist. Some are marketed on a large scale. A flywheel coupled to the vehicle wheels through a speed variation system, such as KERS, is one of them. Unfortunately, this technique requires high speed flywheels to store enough energy and high-techs to stand the centrifugal stress. Applications are limited to specific cases: race cars, frequent stop bus . . . . Differently to the state of art, the patent application U.S. Ser. No. 13/371,697 considers energy storage in the generator rotor, with or without an additional flywheel, driven by the pilot shaft (the 3rd shaft) of a planetary gear mechanism. First, we get a multiplication effect on speed variations thus on stored energy. Second, a speed variation system has not to be provided. Third, same for a system to extract power, which is the Generator stator itself. Consequently, the flywheel speed is moderate and technology is kept basic.
“cylinders on demand” system has similitude with stop and start system. Some engine cylinders are stopped or restarted according to power requirements.
The purpose of the present invention is to improve the here above techniques, at low vehicle speed, particularly regarding costs, efficiency and CO2 emissions.